1. Field of the Invention
This invention relates to an optical device, and more particularly, to an optical transmission device.
2. Description of the Related Art
When an optical device is adjusted to zoom or focus, an optical transmission device will drive a lens group to move to a proper position to achieve required magnification or a focal length.
Referring to FIG. 1, an optical transmission device 6 of an optical device is shown. A driving unit 61 drives a screw 62 to rotate by its axis Y, wherein a nut 63 moves to a base 64 along the axis Y and pushes a lens frame 65, so that the lens frame 65 can move downward and compress a spring 66. On the contrary, when the lens frame 65 is moving away from the base 64, the screw 62 reversely rotates and the nut 63 moves away from the base 64 along the axis Y, and then the spring 66 pushes the lens frame 65 to move away from the base 64. Although the lens frame 65 can be moved by the screw 62 to achieve the object of magnification adjustment and the focusing, the nut 63 entirely contacts the screw 62 when rotating, generating noise due to friction and shaking during the movement process.
To decrease noise generation, another optical transmission device 7 has been disclosed, as shown in FIG. 2. The optical transmission device 7 is controlled by the flexibility and the size of the plastic, to make a sub-clip 71 firmly close toward a main clip 72 and clip a screw 73, wherein the main clip 72 and the sub-clip 71 drives the lens frame 74 to move when the screw 73 rotates. Because both of the main clip 72 and the sub-clip 71 clip the screw 73, noise due to friction and shaking during the movement process is absorbed and noise is decreased. However, because the main clip 72 and the sub-clip 71 are along the radial direction of the screw 73, backlash is easily generated between the main clip 72 along the axis of the screw 73 and the threads of the screw 73, thus decreasing accuracy of the optical transmission device 7. While another optical transmission device has been disclosed, wherein a torsion spring is used for the sub-clip 71 firmly close toward the main clip 72, but accuracy of the optical transmission device is still decreased.